Monsanto's pledge not to commercialise the "terminator" technology that genetically programmes plants to bear sterile seeds was yesterday hailed as a significant victory for developing countries and for farmers around the world, but others dismissed it as little more than a public relations exercise.

"This does not mean that terminator technology is dead," said Hope Shand of the Rural Advancement Foundation in Canada, which has led criticism of the nascent technology since it was patented in March last year.

"Terminator has become synonymous with corporate greed. People instinctively know that sterile seeds are bad for farmers and food security. Not even Monsanto could pretend it was good for anyone except themselves."

In Britain Greenpeace challenged Monsanto, the world's second biggest seed company, to sell it the patent for £1. "Nobody will ever trust a biotech company not to use an invention it owns. If they were really committed to not using it, they could sell it to us. This changes nothing. The shadow is still there."

US patent number 5,723,765 has been the spark that lit a fire under Monsanto and the other GM companies that have been buying up seed companies and moving heavily into farming in poor countries.

The patent for "gene protection" - dubbed terminator by environmental groups when it was approved last year - has united in protest agronomists, agricultural scientists, farmers, environment and development groups, churches, intellectuals and new democracy movements from India to Africa and Latin America.

Fears about GM crops in poor countries concern not food safety, human health or genetic pollution, as in Europe, but the threat to livelihoods.

The vast majority of the world's 500m farmers still collect their best seeds each year and replant them. Preventing a process followed since farming began 10,000 years ago has been seen as endangering their way of life.

The problem for Monsanto and other companies is that in developing countries terminator has become synonymous with GM and a symbol of the increasing control of world agriculture by big foreign corporations.

In Monsanto's version, seeds are soaked in the antibiotic tetracycline, which sets in motion a genetic chain reaction that ultimately instructs the plant to kill its own seeds.

Monsanto's chief executive, Robert Shapiro, in a letter to the Rockefeller Foundation in New York which announced the terminator's development, said the company intended to continue research into sophisticated "trait technologies".

These have been dubbed "terminator 2", or "gene-switchers", and would allow a company to develop crops that grow only if sprayed with a regimen of chemicals that include its herbicides or insecticides.

Monsanto is believed to have 87 terminator patents pending in developing countries but has never used the technology commercially, or even tested it in field trials. The company claims its introduction is five years away. The technology is still in its infancy and most large GM companies are developing their own versions. Thirty-one other terminator patents have been granted.

There are fears that Monsanto may simply be dropping the technology until the political climate improves. Mr Shapiro said Monsanto "did not intend not to commercialise sterile-seed technologies until a full airing of the issues is complete".

The pressure to drop terminator-type technologies has been furious. Last year CGIAR, the world's largest international agricultural research network, said it would boycott all terminator technology. Tens of thousands of individuals from 54 countries wrote to Dan Glickman, the US agriculture secretary, demanding the technology be banned.

The fears about terminator are widespread in developing countries. In the Philippines, Neth Danos of the South-east Asian Regional Institute for Community Education said: "Farmers here know about the terminator and are telling their governments to reject the patent. The terminator could be the greatest threat to the well-being of poor farmers we have ever faced."